1. Field of the Invention
The present invention relates to a method, device, computer program products and a computer readable medium for the correction of static mismatch errors in a D/A converter.
2. Description of the Related Art
Embodiments of the invention relate to methods, devices, computer program products and computer readable media for the correction of static mismatch errors in a D/A (digital-to-analog) converter, where an input word, being the digital representation of an analog input signal, may be divided into one most significant part, a msb-word, and one least significant part, a lsb-word, and where said msb-word may be represented by msb-bits and said lsb-word may be represented by lsb-bits.
The D/A converters (DACs) of interest to embodiments of the invention include the ones that can be referred to as Nyquist converters. In these DACs the output signal typically is created by switching currents between a differential output pair (so called current steering DACs). However the invention also applies to areas where the output signal is generated by switching capacitors or resistors.
The DACs are often divided into segments since the matching requirements between the current sources are higher for the most significant bits of the input word. Consider for instance the 8 most significant bits in a 16 bit converter that have a 1% error in the current. The resulting output current will be:Out-current=(28*0.01*msb-code+lsb-code)*lsb-currentwhich with the input (214+30) corresponds to:out-current=(28*0.01*26+30)*lsb-current˜(28*26+168)that is, the error is 138 lsbs.
But an error in the lsb is much more forgiving:out-current=(28*26+30*0.01)*lsb-current˜(28*26+30.3)i.e. 0.3 lsb.
Since the lsb sources are less sensitive to errors the DACs are often divided into two or three banks (segments) with differently sized reference sources (current sources, resistors, capacitors).
It is known that many DAC suppliers apply various calibration steps at the reference sources; it is for instance known to perform laser trimming of the current sources in high performance DACs. However, it may be more preferable to make error corrections in the digital domain rather than the analog domain.
Accordingly, what is needed are improved methods, systems, and articles of manufacture to improve accuracy of static matching in a DAC.